Brightmare

When Brightmare enters, tap up to one target creature. You gain life equal to that creature's power.

Loyal Pegasus

Flying
Loyal Pegasus can't attack or block alone.

Crested Sunmare

Other Horses you control have indestructible.
At the beginning of each end step, if you gained life this turn, create a 5/5 white Horse creature token.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Starnheim Courser

Flying
Artifact and enchantment spells you cast cost {1} less to cast.

Ronom Unicorn

Sacrifice Ronom Unicorn: Destroy target enchantment.

Archon of Sun's Grace

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Pegasus creatures you control have lifelink.
Constellation — Whenever an enchantment you control enters, create a 2/2 white Pegasus creature token with flying.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on Celestial Unicorn.

Keleth, Sunmane Familiar

Whenever a commander you control attacks, put a +1/+1 counter on it.
Partner (You can have two commanders if both have partner.)

Phyrexian Pegasus

Flying
Whenever Phyrexian Pegasus attacks, another target attacking creature without flying gains flying until end of turn.

Regal Bunnicorn

Regal Bunnicorn's power and toughness are each equal to the number of nonland permanents you control.

Thurid, Mare of Destiny

Flying, lifelink
Whenever you cast a Pegasus, Unicorn, or Horse creature spell, copy it. (The copy becomes a token.)
Other Pegasi, Unicorns, and Horses you control get +1/+1.

Blessed Sanctuary

Prevent all noncombat damage that would be dealt to you and creatures you control.
Whenever a nontoken creature you control enters, create a 2/2 white Unicorn creature token.

Opaline Unicorn

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Pearl Medallion

White spells you cast cost {1} less to cast.

Sungrace Pegasus

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Diamond Mare

As Diamond Mare enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Mesa Unicorn

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Loyal Unicorn

Vigilance
Lieutenant — At the beginning of combat on your turn, if you control your commander, prevent all combat damage that would be dealt to creatures you control this turn. Other creatures you control gain vigilance until end of turn.

Banner of Kinship

As this artifact enters, choose a creature type. This artifact enters with a fellowship counter on it for each creature you control of the chosen type.
Creatures you control of the chosen type get +1/+1 for each fellowship counter on this artifact.